In recent years, aircraft have been maneuvered in what has become known as a "deep stall" condition which effectively stops the forward velocity of an aircraft while maintaining its attitude in a controlled position. One researcher, Dale Reed of NASA Dryden Flight Research Center, has demonstrated the utilization of "deep stall" by moving horizontal stabilizers (or canards) of an aircraft into a 70.degree. nose down attitude just as the aircraft is flown down to a stall speed. This researcher determined that, if the aircraft is moved rapidly from the 18.degree. angle of attack normal stall to about 28.degree., the aircraft does not have sufficent time to roll off onto one wing. The aircraft subsequently falls downward in a horizontal attitude, under complete control of a downward deflected horizontal stabilizer which is not stalled.
The perfection of a "deep stall" procedure offers a significant possibility for landing an aircraft during an emergency situation such as engine flameout. Various means are being investigated to slow the vertical descent of an aircraft while they are in a "deep stall" condition and maintaining proper altitude. A suggested means for accomplishing lowered vertical descent includes the use of small rockets. A further alternative is the utilization of an unfurlable wing extension such as disclosed in co-pending U.S. Patent Application Ser. No. 826,514, assigned to the present assignee. In order to enhance the survival possibility during an emergency landing, various proposals have been made to cushion the landing impact by means such as the previously mentioned rockets as well as airbags deployed from the underside of an emergency landing aircraft. However, although it is possible to maintain proper attitude during "deep stall" and to also decrease the vertical descent of an aircraft during an emergency landing, it is necessary for an aircraft to have a minimum amount of horizontal maneuvering capability prior to landing in order to avoid obstacles such as trees and houses, as well as offering the possibility of landing on a runway if the emergency landing is in the near vicinity of a runway.